CPP magnetic detecting device containing NiFe alloy on free layer thereof

ABSTRACT

A magnetic detecting device having a large ΔRA value is provided. A free magnetic layer has a three layer structure in which a CoFe layer, a Ni a Fe b  alloy layer (here, a and b are represented by at %, and satisfy the relationship of 47≦a≦77 and a+b=100), and a CoFe layer are laminated. 
     In addition, pinned magnetic layers have heusler alloy layers, which are made of a heusler alloy such as a Co 2 MnGe alloy. Accordingly, the product ΔRA of a magnetic resistance variation ΔR of the magnetic detecting device and an area A of the device can have a value of 5 mΩμm 2  more.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a CPP (current perpendicular to theplane) magnetic detecting device in which a sense current flows in thedirection perpendicular to the plane, and more particularly, to amagnetic detecting device in which a product of a magnetic resistancevariation and an area of the device has a large value.

2. Description of the Related Art

FIG. 5 is a partial cross-sectional view showing a conventional magneticdetecting device (spin valve thin film device) taken along the directionparallel to a surface thereof facing a recording medium.

Reference numeral 1 shown in FIG. 5 indicates a base layer made of Ta,and a seed layer 2, which is made of a metal having a body centeredcubic (bcc) structure, such as Cr, is formed on the base layer 1.

A multilayer film T in which an antiferromagnetic layer 3, a pinnedmagnetic layer 4, a nonmagnetic material layer 5, a free magnetic layer6, and a protective layer 7 are laminated in this order, is formed onthe seed layer 2.

The protective layer 7 is made of Ta, the nonmagnetic material layer 5is made of Cu, each of the free magnetic layer 6 and the pinned magneticlayer 4 is made of a NiFe alloy, and the antiferromagnetic layer 3 ismade of PtMn.

Electrode layers 10 are provided on the upper and lower sides of themultilayer film T, respectively, and a DC sense current flows in thedirection perpendicular to the plane of each layer forming themultilayer film T3.

An exchange coupling magnetic field is generated at the interfacebetween the antiferromagnetic layer 3 and the pinned magnetic layer 4,and thus the direction of magnetization of the pinned magnetic layer 4is fixed in a height direction (Y direction in FIG. 5).

Hard bias layers 8 made of hard magnetic material such as CoPt areformed on both sides of the free magnetic layer 6, and the upper andlower portions and end portions of the hard bias layers 8 are insulatedwith insulating layers 9. The free magnetic layer 6 is uniformlymagnetized in the track width direction (X direction in FIG. 5) by thelongitudinal bias magnetic field, which is generated by the hard biaslayers 8.

When an external magnetic field is applied to the magnetic detectingdevice shown in FIG. 5, the direction of magnetization of the freemagnetic layer is changed with respect to that of the pinned magneticlayer. Accordingly, the resistance value of the multilayer film ischanged. When a sense current having a predetermined current valueflows, the change of the resistance value is detected by the change ofthe voltage, thereby detecting the external magnetic field.

There are many cases in which a permalloy having a weak magneticproperty is used as a material of the free magnetic layer of themagnetic detecting device. In addition, an example of a magneticdetecting device having a free magnetic layer, which is made of a NiFealloy other than the permalloy, is disclosed in JP-A-2002-204010(seventh page).

The permalloy is a NiFe alloy containing 80 at % of Ni. Furthermore, asdisclosed in paragraph [0023] in JP-A-2002-204010, the free magneticlayer is made of a Ni_(x)Fe_((100-x)) alloy (40≦x≦70).

However, even if the free magnetic layer is made of the NiFe alloywithin the above-mentioned composition range, it is difficult toincrease the product ΔRA of a magnetic resistance variation of theCPP-GMR magnetic detecting device, in which a DC sense current flows inthe direction perpendicular to the plane of each layer forming themultilayer film, and an area of the device to have a value of 5 mΩμm² ormore, and it is not possible to obtain a practical regenerated output.

SUMMARY OF THE INVENTION

The invention has been made to solve the above-mentioned problems, andit is an object of the invention to provide a magnetic detecting devicehaving a high regenerated output by offering the preferable conditionsfor forming a free magnetic layer.

According to the invention, a magnetic detecting device includes amultilayer film, which has at least one pinned magnetic layer magnetizedin one direction and a free magnetic layer formed on the pinned magneticlayer with a nonmagnetic material layer therebetween, and in which asense current flows in the direction perpendicular to the plane of eachlayer forming the multilayer film. In this case, the free magnetic layerincludes a Ni_(a)Fe_(b) alloy layer (a and b are represented by at %,and satisfy the relationship of 47≦a≦77 and a+b=100). Furthermore, thepinned magnetic layer includes a Co₂YZ alloy layer (Y is one or moreelements of Mn, Fe, and Cr, and Z is one or more elements of Al, Ga, Si,Ge, Sn, In, Sb, Pb, and Zn).

In the invention, the free magnetic layer includes a Ni_(a)Fe_(b) alloylayer, and the pinned magnetic layer includes a Co₂YZ alloy layer.Accordingly, a CPP (current perpendicular to the plane)-GMR magneticdetecting device, in which a sense current flows in the directionperpendicular to the plane of each layer forming the multilayer film,can have a larger and more practical regenerated output than in theconventional CPP-GMR magnetic detecting device or the CIP (current inthe plane)-GMR magnetic detecting device in which a sense current flowsin the direction parallel to the plane of each layer forming themultilayer film.

Specifically, in the invention, a product ΔRA of a resistance variationΔR of the magnetic detecting device and an area A of the device can havea value of 5 mΩμm² or more.

The magnetic detecting layer having a ΔRA value of 5 mΩμm 2 or morecannot be obtained only by forming the free magnetic layer by means of aNiFe alloy containing the content of Ni in the range of 40 to 80 at %.Furthermore, in the CIP-GMR magnetic detecting device that has been putto practical use so far, it has been not possible to obtain theregenerated output corresponding to the CPP-GMR magnetic detectingdevice having a ΔRA value of 5 mΩμm² or more.

In the invention, the free magnetic layer preferably has a three layerstructure in which CoFe layers are laminated on the upper and lowersides of the Ni_(a)Fe_(b) alloy layer, respectively.

The magnetic detecting device of the invention is, for example, a topspin valve CPP-GMR magnetic detecting device in which the pinnedmagnetic layer is provided above the free magnetic layer.

Alternatively, the magnetic detecting device of the invention is, forexample, a bottom spin valve CPP-GMR magnetic detecting device in whichthe pinned magnetic layer is provided below the free magnetic layer.

Furthermore, the magnetic detecting device of the invention is a dualspin valve CPP-GMR magnetic detecting device in which the nonmagneticmaterial layer and the pinned magnetic layer are provided below the freemagnetic layer and another nonmagnetic material layer and another pinnedmagnetic layer are provided above the free magnetic layer. For example,an antiferromagnetic layer overlaps the pinned magnetic layer.

In the invention, the free magnetic layer includes a Ni_(a)Fe_(b) alloylayer (a and b are represented by atomic %, and satisfy the relationshipof 47≦a≦77 and a+b=100), and the pinned magnetic layer includes a Co₂YZalloy layer. Accordingly, a CPP-GMR magnetic detecting device, in whicha sense current flows in the direction perpendicular to the plane ofeach layer forming the multilayer film, can have a larger and morepractical regenerated output than in the conventional CPP-GMR magneticdetecting device or the CIP (Current In the plane)-GMR magneticdetecting device in which a sense current flows in the directionparallel to the plane of each layer forming the multilayer film.

In the invention, a product ΔRA of a resistance variation ΔR of themagnetic detecting device and an area A of the device can have a valueof 5 mΩμm² or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of a magneticdetecting device (single spin valve magnetoresistive sensor) accordingto a first embodiment of the invention as seen from the surface thereoffacing a recording medium;

FIG. 2 is a cross-sectional view showing the structure of a magneticdetecting device (dual spin valve magnetoresistive sensor) according toa second embodiment of the invention as seen from the opposite side to arecording medium;

FIG. 3 is a cross-sectional view showing the structure of a magneticdetecting device (single spin valve magnetoresistive sensor) accordingto a third embodiment of the invention as seen from the opposite side toa recording medium;

FIG. 4 is a graph showing the product ΔRA of the magnetic resistancevariation ΔR of the magnetic detecting device and the area A of thedevice when the dual spin valve magnetic detecting device is providedand the content of Ni (represented by at %) in a Ni_(a)Fe_(b) alloylayer (here, a and b are represented by at %, and satisfy therelationship of a+b=100) forming a free magnetic layer is changed; and

FIG. 5 is a cross-sectional view showing a conventional magneticdetecting device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a cross-sectional view showing the entire structure of amagnetic detecting device (single spin valve magnetoresistive sensor)according to a first embodiment of the invention, as seen from thesurface thereof facing a recording medium. Furthermore, in FIG. 1, thedevice extending in the X direction is shown by a cross section at theonly central portion thereof.

The single spin valve magnetoresistive sensor is provided to thetrailing end portion of a floating slider, which is provided to a harddisk unit, and detects the recording magnetic field of a hard disk orthe like. In addition, a magnetic recording medium such as a hard diskmoves in the Z direction, and the leak magnetic field from the magneticrecording medium is formed in the Y direction.

The lowermost layer in FIG. 1 is a base layer, which is made of anonmagnetic material such as one or more elements of Ta, Hf, Zr, Ti, Mo,and W. A multilayer film T1, which includes a sheet layer 12, anantiferromagnetic layer 13, a pinned magnetic layer 14, a nonmagneticmaterial layer 15, a free magnetic layer 16, and a protective layer 17,is laminated on the base layer 11. The magnetic detecting device shownin FIG. 1 is a so-called bottom spin valve GMR magnetic detecting devicein which the antiferromagnetic layer 13 is provided below the freemagnetic layer 16.

The sheet layer 12 is made of NiFeCr or Cr. When the sheet layer 12 ismade of NiFeCr, the sheet layer 12 has a face centered cubic (fcc)structure and an equivalent crystal plane indicated as a {111} plane ispreferentially oriented in the direction parallel to the plane. Inaddition, when the sheet layer 12 is made of Cr, the sheet layer 12 hasa body centered cubic (bcc) structure and an equivalent crystal planeindicated as a {110} plane is preferentially oriented in the directionparallel to the plane.

Furthermore, although the base layer 11 has an almost amorphousstructure, the base layer 11 may not be formed.

The antiferromagnetic layer 13 formed on the sheet layer 12 may be madeof an antiferromagnetic material containing Mn and an element X (here,the element X is one or more elements of Pt, Pd, Ir, Rh, Ru, and Os).

The antiferromagnetic layer 13 has a face centered cubic (fcc)structure, or a face centered tetragonal (fct) structure.

An X—Mn alloy using platinum group elements has excellentcharacteristics of the antiferromagnetic material, which has anexcellent corrosion resistance, a high blocking temperature, a largeexchange coupling magnetic field (Hex), and the like. For example, aPtMn alloy or an IrMn, which are formed in a binary system, can be usedas the X—Mn alloy.

Further, in the invention, the antiferromagnetic layer 13 may be made ofan antiferromagnetic material containing Mn, the element X, and anelement X′ (here, the element X′ is one or more elements of Ne, Ar, Kr,Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge,Zr, Nb, Mo, Ag, Cd, Sn, Hf, Ta, W, Re, Au, Pb, and rare earth elements).

Moreover, an element, which is penetrated into the gap of the spacelattice composed of the element X and Mn or is substituted with a partof lattice points of the crystal lattice composed of the element X andMn, is preferably used as the element X′. Here, a solid solution means asolid in which ingredients are uniformly mixed.

In the invention, it is preferable that the content of the element X′ bein the composition range of 0.2 to 10 at % (atomic %), and it is morepreferable that the content of the element X′ be in the compositionrange of 0.5 to 5 at %. Further, in the invention, it is preferable thatthe content of the element X be Pt or Ir.

In the invention, it is preferable that the content of the element X orelements X+X′ of the antiferromagnetic layer 13 be set in the range of45 to 60 at %. It is more preferable that the content of the element Xor elements X+X′ of the antiferromagnetic layer 13 be set in the rangeof 49 to 56.5 at %. Accordingly, in the process of forming a film, theinterface between the antiferromagnetic layer and the pinned magneticlayer 14 is in the noncoherent state, and it is conjectured that theantiferromagnetic layer 13 causes an appropriate order transformation tooccur by the heat treatment.

The pinned magnetic layer 14 formed on the antiferromagnetic layer 13has a three layer structure.

The pinned magnetic layer 14 has the three layer structure, which iscomposed of a magnetic layer 14 a, a nonmagnetic intermediate layer 14b, and a magnetic layer 14 c. The directions of magnetization of themagnetic layer 14 a and the magnetic layer 14 c are in the mutuallyantiparallel state by the exchange coupling magnetic field at theinterface between the antiferromagnetic layer 13 and the pinned magneticlayer, and the antiferromagnetic exchange coupling magnetic field (RKKYinteraction) caused by the nonmagnetic intermediate layer 14 b. Thisstate is called as an artificial ferrimagnetic coupling state, and thepinned magnetic layer 14 can be stably magnetized by this structure.Furthermore, it is possible to increase the exchange coupling magneticfield, which is generated at the interface between the pinned magneticlayer and the antiferromagnetic layer 13.

However, the pinned magnetic layer 14 may have a monolayer structuremade of a magnetic material, or a multilayer structure made of amagnetic material.

In addition, the magnetic layer 14 a is formed so as to have a thicknessof, for example, about 15 to 35 Å, the nonmagnetic intermediate layer 14b is formed so as to have a thickness of about 8 to 10 Å, and themagnetic layer 14 a is formed so as to have a thickness of about 20 to50 Å.

The nonmagnetic intermediate layer 14 b is made of a nonmagneticconductive material such as Ru, Rh, Ir, Cr, Re, and Cu.

Furthermore, it is preferable that the magnetic layer 14 c of the pinnedmagnetic layer 14 be a Co₂YZ alloy layer (Y is one or more elements ofMn, Fe, and Cr, and Z is one or more elements of Al, Ga, Si, Ge, Sn, In,Sb, Pb, and Zn). The Co₂YZ alloy layer has the characteristic of asemimetal, and is an effective material to increase the product ΔRA ofthe magnetic resistance variation ΔR of a CPP (current perpendicular tothe plane)-GMR magnetic detecting device and the area A of the device.

The nonmagnetic material layer 15 formed on the pinned magnetic layer 14is made of Cu, Au, or Ag.

Moreover, the free magnetic layer 16 is formed on the nonmagneticmaterial layer. The structure of the free magnetic layer 16 will bedescribed below.

In the embodiment shown in FIG. 1, hard bias layers 18 are formed onboth sides of the free magnetic layer 16. The free magnetic layer 16 isuniformly magnetized in the track width direction (X direction inFIG. 1) by the longitudinal bias magnetic field, which is generated bythe hard bias layers 18. Each of the hard bias layers 18 is made of, forexample, a Co—Pt (cobalt-platinum) alloy, a Co—Cr—Pt(cobalt-chrome-platinum) alloy, or the like.

The upper and lower portions and end portions of the hard bias layers 18are insulated with insulating layers 19 made of alumina or the like.

Electrode layers 20 are provided on the upper and lower sides of themultilayer film T1, respectively. Accordingly, a CPP-GMR magneticdetecting device in which a sense current flows in the directionperpendicular to the plane of each layer forming the multilayer film T1,is obtained.

Each of the electrode layers 20 is made of α-Ta, Au, Cr, Cu (copper),Rh, Ir, Ru, W (tungsten), or the like.

The characteristics of the present embodiment will be described.

The free magnetic layer 16 has the three layer structure in which a CoFelayer 16 a, a Ni_(a)Fe_(b) alloy layer 16 b (here, a and b arerepresented by at %, and satisfy the relationship of 47≦a≦77 anda+b=100), and a CoFe layer 16 c are laminated in this order from thelower side.

The CoFe layer 16 a and the CoFe layer 16 c, which are laminated on theupper and lower sides of the Ni_(a)Fe_(b) alloy layer 16 b,respectively, are provided to prevent the diffusion of the NiFe alloyand to reduce the magnetostriction of the entire free magnetic layer 16.Meanwhile, even though only the CoFe layer 16 a being in contact withthe nonmagnetic material layer 15 is provided in case of the single spinvalve GMR magnetic detecting device shown in FIG. 1, it is possible toprevent the diffusion of the NiFe alloy into the nonmagnetic materiallayer 15 and to reduce the magnetostriction of the entire free magneticlayer 16. In addition, the CoFe layers 16 a and 16 c are not providedand the free magnetic layer 16 may have a single-layer structure that iscomposed of only the Ni_(a)Fe_(b) alloy layer 16 b.

Further, it is preferable that the thickness t1 of the Ni_(a)Fe_(b)alloy layer 16 b be in the range of 20 to 90 Å, and it is preferablethat the thickness t2 of the CoFe layer 16 a and the thickness t3 of theCoFe layer 16 c be in the range of 3 to 15 Å.

In the spin valve thin film device shown in FIG. 1, after all layersfrom the base layer 11 to the protective layer 17 are laminated, a heattreatment is performed to generate the exchange coupling magnetic fieldat the interface between the antiferromagnetic layer 13 and the pinnedmagnetic layer 14. In this case, since the magnetic field is formed inthe direction parallel to the Y direction in FIG. 1, the pinned magneticlayer 14 is magnetized in the direction parallel to the Y direction inFIG. 1. Furthermore, the pinned magnetic layer 14 has an artificialferrimagnetic structure in the embodiment shown in FIG. 1. Accordingly,if the magnetic layer 14 a is magnetized, for example, in the Ydirection, the magnetic layer 14 c and the magnetic layer 23 aremagnetized in the direction reverse to the Y direction.

In the magnetic detecting device shown in FIG. 1, the pinned magneticlayer and the free magnetic layer are magnetized in the directionorthogonal to each other. The leak magnetic field from the magneticrecording medium is penetrated into the magnetic detecting device in theY direction, and thus the direction of magnetization of the freemagnetic layer is changed with high sensitivity. An electricalresistance value changes depending on the relation between the change ofthe direction of magnetization of the free magnetic layer and thedirection of fixed magnetization of the pinned magnetic layer. Then, avoltage value and a current value change on the basis of the change ofthe electrical resistance value, and thus the leak magnetic field fromthe magnetic recording medium is detected.

FIG. 2 is a partial cross-sectional view showing the structure of a dualspin valve magnetic detecting device according to the invention.

As shown in FIG. 2, a base layer 11, a seed layer 12, anantiferromagnetic layer 13, a pinned magnetic layer 31, a nonmagneticmaterial layer 15, and a free magnetic layer 16 are successivelylaminated from the lower side. In addition, a nonmagnetic material layer15 and a pinned magnetic layer 32, an antiferromagnetic layer 13, and aprotective layer 17 are successively laminated on the free magneticlayer 16 so as to form a multilayer film T2.

Furthermore, hard bias layers 18 are formed on both sides of the freemagnetic layer 16. The hard bias layers 18 are insulated with insulatinglayers 19 made of alumina or the like.

Electrode layers 20 are provided on the upper and lower sides of themultilayer film T2, respectively. Accordingly, a CPP-GMR magneticdetecting device in which a sense current flows in the directionperpendicular to the plane of each layer forming the multilayer film T2,is obtained.

Moreover, in FIG. 2, layers indicated by the same reference numerals asthose in FIG. 1 are made of the same materials as those of the layers inFIG. 1, respectively.

The pinned magnetic layer 31 of the magnetic detecting device shown inFIG. 2 has a four-layer structure, which is composed of a magnetic layer31 a, a nonmagnetic intermediate layer 31 b, a magnetic layer 31 c, anda heusler alloy layer 31 d. Each of the magnetic layer 31 a and themagnetic layer 31 c is made of a ferromagnetic material such as CoFe,and the heusler alloy layer 31 d is made of a heusler alloy to bedescribed below. The heusler alloy layer 31 d has a ferromagneticproperty, and the magnetic layer 31 c and the heusler alloy layer 31 dare magnetized in the same direction with each other by a ferromagneticcoupling.

The direction of magnetization of the magnetic layer 31 a, and thedirections of magnetization of the magnetic layer 31 c and the heusleralloy layer 31 d are in the mutually antiparallel state by the exchangecoupling magnetic field at the interface between the antiferromagneticlayer 13 and the pinned magnetic layer, and the antiferromagneticexchange coupling magnetic field (RKKY interaction) caused by thenonmagnetic intermediate layer 31 b.

The heusler alloy layer 31 d is provided in the pinned magnetic layer 31of the CPP-GMR magnetic detecting device, and a heusler alloy layer 32 ais provided in the pinned magnetic layer 32. Accordingly, after andbefore the external magnetic field is applied to the device, the spindiffusion length or a variation of the mean free path of conductionelectrons in the multilayer film T2 increase. That is, the variation ofthe resistance value of the multilayer film T2 increases, and thedetection sensitivity for the external magnetic field improves. Inaddition, the heusler alloy layer may be laminated below the nonmagneticintermediate layer 31 b or above a nonmagnetic intermediate layer 32 c.However, since layers being in contact with the nonmagnetic materiallayers 15 contribute to the magnetoresistance effect, it is effectivethat the heusler alloy layer is laminated above the nonmagneticintermediate layer 31 b or below the nonmagnetic intermediate layer 32c.

The heusler alloy layer 31 d, which is one of the layers forming thepinned magnetic layer 31, is a Co₂YZ alloy layer (Y is one or moreelements of Mn, Fe, and Cr, and Z is one or more elements of Al, Ga, Si,Ge, Sn, In, Sb, Pb, and Zn). The Co₂YZ alloy layer has thecharacteristic of a semimetal, and is an effective material to increasethe product ΔRA of the magnetic resistance variation ΔR of a CPP-GMRmagnetic detecting device and the area A of the device.

More preferably, the heusler alloy layer 31 d is made of a metal complexhaving the composition formula represented by Co₂MnZ. Here, Z is one ormore elements of Al, Ga, Si, Ge, Sn, In, Sb, Pb, and Zn.

The pinned magnetic layer 32 of the magnetic detecting device shown inFIG. 2 has a four-layer structure, which is composed of the heusleralloy layer 32 a, a magnetic layer 32 b, the nonmagnetic intermediatelayer 32 c, and a magnetic layer 32 d. Each of the magnetic layer 32 band the magnetic layer 32 d is made of a ferromagnetic material such asCoFe, and the heusler alloy layer 32 a is made of a heusler alloy thatis the same material as that of the heusler alloy layer 31 d of theabove-mentioned pinned magnetic layer 31. The magnetic layer 32 b has aferromagnetic property, and the heusler alloy layer 32 a and themagnetic layer 32 b are magnetized in the same direction with each otherby a ferromagnetic coupling.

The direction of magnetization of the magnetic layer 32 d, and thedirections of magnetization of the heusler alloy layer 32 a and themagnetic layer 32 b are in the mutually antiparallel state by theexchange coupling magnetic field at the interface between theantiferromagnetic layer 13 formed on the pinned magnetic layer 32 andthe pinned magnetic layer, and the antiferromagnetic exchange couplingmagnetic field (RKKY interaction) caused by the nonmagnetic intermediatelayer 32 c.

Furthermore, each of the pinned magnetic layers 31 and 32 may not havean artificial ferrimagnetic structure. In addition, the pinned magneticlayer 31 shown in FIG. 2 may be used instead of the pinned magneticlayer 14 of the magnetic detecting device shown in FIG. 1.

In the present embodiment, the free magnetic layer 16 has the threelayer structure in which a CoFe layer 16 a, a Ni_(a)Fe_(b) alloy layer16 b (here, a and b are represented by at %, and satisfy therelationship of 47≦a≦77 and a+b=100), and a CoFe layer 16 c arelaminated in this order from the lower side.

The CoFe layer 16 a and the CoFe layer 16 c, which are laminated on theupper and lower sides of the Ni_(a)Fe_(b) alloy layer 16 b,respectively, are provided to prevent the diffusion of the NiFe alloyand to reduce the magnetostriction of the entire free magnetic layer 16.Meanwhile, the CoFe layers 16 a and 16 c are not provided and the freemagnetic layer 16 may have a single-layer structure, which is composedof only the Ni_(a)Fe_(b) alloy layer 16 b.

Further, it is preferable that the thickness t1 of the Ni_(a)Fe_(b)alloy layer 16 b be in the range of 20 to 90 Å, and it is preferablethat the thickness t2 of the CoFe layer 16 a and the thickness t3 of theCoFe layer 16 c be in the range of 3 to 15 Å.

In the spin valve thin film device shown in FIG. 2, after all layersfrom the base layer 11 to the protective layer 17 are laminated, a heattreatment is performed to generate the exchange coupling magnetic fieldat the interfaces between the antiferromagnetic layer 13 and the pinnedmagnetic layers 31 and 32. In this case, since the magnetic field isformed in the direction parallel to the Y direction in FIG. 2, thepinned magnetic layers 31 and 32 are magnetized in the directionparallel to the Y direction in FIG. 2. Furthermore, each of the pinnedmagnetic layers 31 and 32 has an artificial ferrimagnetic structure inthe embodiment shown in FIG. 2.

In the magnetic detecting device shown in FIG. 2, each of the pinnedmagnetic layer and the free magnetic layer are magnetized in thedirection orthogonal to each other. The leak magnetic field from themagnetic recording medium is penetrated into the magnetic detectingdevice in the Y direction, and thus the direction of magnetization ofthe free magnetic layer is changed with high sensitivity. An electricalresistance value changes depending on the relation between the change ofthe directions of magnetization of the free magnetic layer and thedirection of fixed magnetization of each pinned magnetic layer. Then, avoltage value and a current value change on the basis of the change ofthe electrical resistance value, and thus the leak magnetic field fromthe magnetic recording medium is detected. In the dual spin valvemagnetic detecting device, the pinned magnetic layers 31 and 32 areprovided above and below the free magnetic layer 16 with the nonmagneticmaterial layers 15 therebetween, respectively. Accordingly, the productΔRA of the magnetic resistance variation ΔR and the area A of the devicecan be theoretically increased twice as large as the product in the spinvalve magnetic detecting device shown in FIG. 1. According to themagnetic detecting device of the present embodiment, the ΔRA of themagnetic detecting device can have a value of 5 mΩμm² or more.

FIG. 3 is a partial cross-sectional view showing the structure of a topspin valve magnetic detecting device according to the invention.

As shown in FIG. 3, a base layer 11, a seed layer 12, a free magneticlayer 16, a nonmagnetic material layer 15, a pinned magnetic layer 32,an antiferromagnetic layer 13, and a protective layer 17 aresuccessively laminated so as to form a multilayer film T3.

Furthermore, hard bias layers 18 are formed on both sides of the freemagnetic layer 16. The hard bias layers 18 are insulated with insulatinglayers 19 made of alumina or the like.

Electrode layers 20 are provided on the upper and lower sides of themultilayer film T3, respectively. Accordingly, a CPP-GMR magneticdetecting device in which a sense current flows in the directionperpendicular to the plane of each layer forming the multilayer film T3,is obtained.

Moreover, in FIG. 3, layers indicated by the same reference numerals asthose in FIG. 1 or 2 are made of the same materials as those of thelayers in FIG. 1 or 2, respectively.

In the present embodiment, the free magnetic layer 16 has the threelayer structure in which a CoFe layer 16 a, a Ni_(a)Fe_(b) alloy layer16 b (here, a and b are represented by at %, and satisfy therelationship of 47≦a≦77 and a+b=100), and a CoFe layer 16 c arelaminated in this order from the lower side.

Furthermore, in FIGS. 1 to 3, the directions of magnetization of thepinned magnetic layers 14, 31, and 32 are fixed by the exchange couplingmagnetic fields at the interface between the antiferromagnetic layer 13and the pinned magnetic layers 14, 31, and 32. However, each of thepinned magnetic layers 14, 31, and 32 may have a self-pinned structurein which the antiferromagnetic layer 13 does not overlap the pinnedmagnetic layers 14, 31, and 32, and the directions of magnetization ofthe pinned magnetic layers 14, 31, and 32 are fixed by the uniaxialanisotropy of the pinned magnetic layers 14, 31, and 32.

FIRST EXAMPLE

When the dual spin valve magnetic detecting device to be described belowis provided and the content of Ni (represented by at %) in aNi_(a)Fe_(b) alloy layer (here, a and b are represented by at %, andsatisfy the relationship of a+b=100) forming a free magnetic layer ischanged, the product ΔRA of the magnetic resistance variation ΔR of themagnetic detecting device and the area A of the device is measured. Inaddition, a product ΔRA in the magnetic detecting device according to anexample, and a product ΔRA in the magnetic detecting device according toa comparative example are measured and compared with each other. In theexample, each of the second pinned magnetic layers (corresponding to themagnetic layer 31 c and the heusler alloy layer 31 d, and the heusleralloy layer 32 a and the magnetic layer 32 b in FIG. 2) is made of aCo₂MnGe alloy. In the comparative example, each of the second pinnedmagnetic layers is made of only a CoFe alloy.

The example: substrate/base layer Ta (30 Å)/seed layer NiFeCr (50Å)/antiferromagnetic layer IrMn (70 Å)/pinned magnetic layers (firstpinned magnetic layer Co₇₀Fe₃₀ (30 Å)/nonmagnetic intermediate layer Ru(9.1 Å)/second pinned magnetic layer CoFe (10 Å)/Co₂MnGe (40Å))/nonmagnetic material layer Cu (43 Å)/free magnetic layer CoFe (5Å)/Ni_(a)Fe_(b) (90 Å)/CoFe (5 Å)/nonmagnetic material layer Cu (43Å)/second pinned magnetic layer (Co₂MnGe (40 Å)/CoFe (10 Å)/nonmagneticintermediate layer Ru (9.1 Å)/first pinned magnetic layer (Co₇₀Fe₃₀ (30Å))/antiferromagnetic layer IrMn (70 Å)/protective layer Ta (200 Å).Here, a number in a parenthesis is a thickness value of each layer.

The comparative example: substrate/base layer Ta (30 Å)/seed layerNiFeCr (50 Å)/antiferromagnetic layer IrMn (70 Å)/pinned magnetic layers(first pinned magnetic layer Co₇₀Fe₃₀ (30 Å)/nonmagnetic intermediatelayer Ru (9.1 Å)/second pinned magnetic layer CoFe (50 Å)/nonmagneticmaterial layer Cu (43 Å)/free magnetic layer CoFe (5 Å)/Ni_(a)Fe_(b) (90Å)/CoFe (5 Å)/nonmagnetic material layer Cu (43 Å)/second pinnedmagnetic layer (CoFe (50 Å))/nonmagnetic intermediate layer Ru (9.1Å)/first pinned magnetic layer (Co₇₀Fe₃₀ (30 Å))/antiferromagnetic layerIrMn (70 Å)/protective layer Ta (200 Å). Here, a number in a parenthesisis a thickness value of each layer.

The results are shown in FIG. 4. In the magnetic detecting deviceaccording to the example in which each of the second pinned magneticlayers includes a layer made of a Co₂MnGe alloy, when the content a ofNi in the Ni_(a)Fe_(b) alloy layer (here, a and b are represented by at%, and satisfy the relationship of a+b=100) is in the range of 17 to 77at %, the ΔRA of the magnetic detecting device has a value of 5 mΩμm² ormore.

Meanwhile, in the magnetic detecting device according to the comparativeexample in which each of second pinned magnetic layers is made of a CoFealloy, the maximum ΔRA of the magnetic detecting device has a value of 2mΩμm² or less, and the regenerated output thereof only has a value lowerthan the half of that of the magnetic detecting device according to theexample.

In the conventional CPP-GMR magnetic detecting device, the ΔRA of themagnetic detecting device cannot have a value of 5 mΩμm ² or more.Furthermore, in the CIP-GMR magnetic detecting device that has been putto practical use so far, it has been not possible to obtain theregenerated output corresponding to the CPP-GMR magnetic detectingdevice having a ΔRA value of 5 mΩμm² or more.

In contrast, the CPP-GMR magnetic detecting device according to theexample can have a ΔRA value of 5 mΩμm² or more. That is, in themagnetic detecting device according to the example, it is possible toobtain a larger and more practical regenerated output than in theconventional CPP-GMR magnetic detecting device or the CIP-GMR magneticdetecting device.

1. A magnetic detecting device comprising: a multilayer film, which hasat least one pinned magnetic layer magnetized in one direction and afree magnetic layer formed on the pinned magnetic layer with anonmagnetic material layer therebetween, and in which a sense currentflows in the direction perpendicular to the plane of each layer formingthe multilayer film, wherein the free magnetic layer includes aNi_(a)Fe_(b) alloy layer (a and b are represented by at %, and satisfythe relationship of 47≦a≦77 and a+b=100), the pinned magnetic layerincludes a Co₂YZ alloy layer (Y is one or more elements of Mn, Fe, andCr, and Z is one or more elements of Al, Ga, Si, Ge, Sn, In, Sb, Pb, andZn), and wherein the Co₂YZ alloy has a Heusler structure.
 2. Themagnetic detecting device according to claim 1, wherein a product ΔRA ofa resistance variation and an area of the device has a value of 5 mΩ/μm²or more.
 3. The magnetic detecting device according to claim 1, whereinthe free magnetic layer has a three layer structure in which CoFe layersare laminated on the upper and lower sides of the Ni_(a)Fe_(b) alloylayer, respectively.
 4. The magnetic detecting device according to claim1, wherein the pinned magnetic layer is provided above the free magneticlayer.
 5. The magnetic detecting device according to claim 1, whereinthe pinned magnetic layer is provided below the free magnetic layer. 6.The magnetic detecting device according to claim 1, wherein thenonmagnetic material layer and the pinned magnetic layer are providedbelow the free magnetic layer, and another nonmagnetic material layerand another pinned magnetic layer are also provided above the freemagnetic layer.
 7. The magnetic detecting device according to claim 4,wherein an antiferromagnetic layer overlaps the pinned magnetic layer.